So-called wiring boards are used in a conventional method of producing a cable harness, particularly for motor vehicles. The later course of the cable harness on a wiring board is predetermined. The individual wires are successively secured to the wiring board with the aid of mechanical fixing elements.
A cable harness is typically equipped with connecting elements, such as plugs or bushings. The individual wires are usually wound with the aid of adhesive tape for ensuring that the individual wires will remain bundled. In many cases, this type of fixing or jacketing is inadequate. In these instances, the cable harness is inserted into an injection mold and cast or foamed with a plastic material.
Clearly, this type of manufacturing method is very labor- and cost-intensive. Therefore, different alternative manufacturing methods have been proposed; these have been used especially for smaller cable harnesses or flat cable harnesses. For example, DE 27 58 491 discloses a method of producing a flat cable harness, in which a film is produced from a granulated, thermoplastic hot-melt plastic adhesive. In an insertion apparatus, the individual wires of a flat cable harness are positioned parallel to one another, and the hot-melt adhesive film is laid over the lines. Due to a slight pressure in a heating apparatus, the hot-melt adhesive is melted onto the lines.
DE 27 58 472 discloses a method of producing a flat cable harness, in which the individual wires, which are already provided with an insulation, are arranged between two layers of film, with the film layers being connected to one another through a high-frequency welding method.
DE 37 40 593 C2 describes a method in which the cable harness or a wiring arrangement is integrated into a door frame. The door frame comprises a synthetic resin. The lines constituting the wiring arrangement are either laid in grooves of the synthetic-resin door frame, embedded in the synthetic-resin material through ultrasonic welding or etched onto the surface of the door frame.
It is the object of the invention to propose an alternative method of producing a cable harness, with which even cable harnesses of a complex nature can be produced, and which is not only suited for a separate cable harness production, but also for the construction of a cable harness directly on a vehicle component. Furthermore, the method is intended to be virtually completely automated.
This object is accomplished by a method in which an essentially strip-shaped base layer, which follows the later course of the cable harness, at least in sections, is applied to the assembly side of an assembly support. The base layer adheres, at least temporarily, to the assembly support. The base layer is preferably automatically put in place with the aid of a robot. The wires are also laid on the base layer by a robot. It is conceivable that a laying head removes the individual wires from a wire magazine and lays them, individually or several at a time, essentially parallel on the base layer. From this point on, the term wires encompasses any type of electrical conductors, such as flat bands, metallically conductive or metallically coated plastics, waveguides, metallic film conductors or the like.
As the third method step, a cover layer comprising a liquid or molten plastic material is sprayed, extruded, poured or brushed onto a wire layer produced, for example, in the described manner, or a granulated or powdered plastic material is applied and subsequently treated in the manner of a sintering process with heat, ultrasound or the like; in the process, the plastic material envelops the wires, adheres to the base layer and hardens, or generally converts to a more solid consistency. Whenever the term liquid plastic material is used in this description, it is also meant to encompass dual-component plastics. An example of such a plastic is polyurethane. The initial mixture of this type of plastic includes two components (olefin and cyanide components) that react with one another as soon as they are mixed together. Assuming the simplest case, in which the base layer and the cover layer comprise the same material, the production of a single- or multi-layer cable harness would merely necessitate a robot-guided application head for the plastic mass and a laying apparatus for the individual wires.
According to another aspect of the invention, the assembly support itself constitutes the vehicle component, for example a vehicle door. In such a case, the base layer remains fixed to the vehicle component. This fixing can be attained solely through the adhesive properties of the cooperating materials. To support the adhesive or material-to-material adherence, the vehicle component can have undercuts, such as interlacings or depressions, which are filled with plastic material when the base layer is applied, thereby assuring an additional mechanical connection or a form fit between the base layer and the vehicle component.
Numerous automobile manufacturers are demanding an increasing level of completion from their suppliers. In view of these demands, suppliers are offering complete assemblies that essentially need only be mounted to the vehicle body in the manufacturing plant. An example of such a component is a vehicle door or a tail gate. With the method according to this aspect, it is conceivable to manufacture the cable harness directly on the component in the supplier""s plant.
The assembly support can, however, also be an assembly template, for example in the form of a table, a roller or a production band, with the tabletop, the top of the production band or the circumferential surface of the roller respectively forming the assembly side. In such a procedure, it is advisable for a separating layer to be applied to the assembly support, for example sprayed or brushed on, before the base layer is applied; this separating layer permits the completed cable harness to be released from the assembly support. The respectively used separating means depends on the base layer/assembly support material pairing, and, accordingly, varies from case to case.
The base layer is preferably produced as follows: First, a liquid plastic mass is sprayed, poured, extruded or brushed onto the assembly support; afterward, the plastic mass converts to a more solid consistency, or at least hardens to a certain extent. Furthermore, the base layer can be produced as described above for the cover layerxe2x80x94a granulated or powdered plastic material is applied, and the application of heat, ultrasound or the like subsequently effects a sort of sintering of the plastic particles.
As mentioned above, the same material used for a cover layer can also be used for the base layer, so the above description relating to the material of the cover layer also applies here. For example, a quick-curing plastic can be used, that is, one that reaches its ultimate consistency shortly after being applied. An example of this type of plastic is a polyurea spray elastomer. The material is a relatively thin initial mixture of two components that react with one another (isocyanate and secondary or tertiary amine); they are brought into contact with one another, or are mixed, in a mixer shortly before being applied to the assembly support. A plastic melt or the initial mixture of a dual-component plastic can be used to produce the base layer. An example of this type of plastic is polyurethane. The base layer should typically have a predetermined width. In the case of plastics that do not harden very quickly, an appropriate tool prevents the plastic melt or liquid initial mixture from flowing out. The plastic melt or the initial mixture is, however, preferably thixotropically set, which essentially prevents an applied plastic band from flowing out.
A prefabricated base band embodied in the manner of an adhesive tape or a film blank can also be used as the base layer. A base band of this type can either be affixed mechanically to the assembly support or possibly affixed beneath a separating layer. In an especially preferred embodiment, further wires are laid on the first cover layer and a further cover layer is applied. This cover layer can comprise the same material as the first cover layer. It can, however, consist of a different material, for example if the cover layer also serves as a mechanical protection and, correspondingly, should have a greater mechanical resistance. It is also conceivable that the material of the final cover layer has a greater chemical resistance to the operating materials of a motor vehicle than a lower cover layer or the base layer. The described method can be repeated multiple times for the construction of multi-layer cable harnesses.
The wires can be laid on the base layer or the base band, on the one hand, and on a cover layer, on the other hand, in different ways. In the case of quick-curing plastics, it is advisable to lay the wires with the aid of an adhesive. For this purpose, an adhesive is applied to the corresponding, hardened or solidified layer in accordance with a suitable method, and the wires are laid on this adhesive layer. The wires can also be self-adhesive; for example, they can be sprayed with an adhesive prior to being laid. With an appropriate selection of the plastic, the wires can be fixed to a base or cover layer through high-frequency or ultrasonic welding. With thermoplastic plastics, the respective layer can be warmed, which at least partially sinks the wires into the warmed layer material and embeds them.
The connecting elements that are usually present on a cable harness can be mounted as follows: The electrical connecting elements are preferably fixed, either permanently or detachably, to the assembly support before the base layer or base band is applied. The electrical connecting elements are prepared such that their electrical contact elements, which are preferably embodied as insulation displacement contacts, are freely accessible for producing the electrical-mechanical connection between the wire ends and the contact elements. Connecting elements having a clamshell housing, for example, can be used to assure this accessibility. The one housing half, which supports the electrical contact elements, is fixed in a recess or hole in the assembly support.
Another option is to fix the housing halves to the assembly support with the use of a vacuum. The wires of the first wire layer are laid after the base layer has been applied to the assembly support; the cable ends of the wire ends are preferably pressed into the insulation displacement contacts of the connecting elements automatically, that is, by the laying apparatus itself.
Before the last cover layer is applied, the electrical connecting elements are completed by the positioning of the second housing half. To seal the housing, it can be advisable to envelop the housing, at least in the region of its separation joint, with plastic material, for example when a closing cover layer is applied. The final cover layer is then applied. If it is necessary to provide a longitudinal water seal, the transition region between the electrical connecting element and the cable harness can be enveloped with the material of the closing cover layer. An alternative method is to omit the second housing half and provide a hermetic seal of the connecting elements by introducing the cover-layer material into the half-shell-type housing of the connecting element when the closing cover layer is applied.